The ability to efficiently store and retrieve data is an essential component of any integrated electronic system. In recent years, the development of optical storage systems has allowed greater storage densities than previously known. An important concern of any storage media, including optical storage media, is the time required to access the storage system to either store or retrieve data.
Optical storage media are currently used in a variety of forms. Optical disks, rectangular optical media, and optical tape are some of these forms. In each of these forms of optical storage media, a laser is used to write and read from the optical storage media. In general, the beam of light is directed from laser to the surface of the optical storage media where it is reflected. The reflected beam of light is routed to a detector which can read the data stored on the optical storage media responsive to the receipt of the reflected beam.
The methods and apparatus used to direct the beam of light to the appropriate section of the optical storage media are by far the slowest portion of the data storage and recovery system. For example, the typical optical storage disk drive available currently have on the order of 35 to 100 millisecond access times including a rotational latency of approximately 16 milliseconds. In comparison, the controllers associated with these systems are working with an overhead of approximately one milli-second. Accordingly, there is approximately a two order of magnitude difference between the mechanical access time of the optical storage drives and the remaining circuitry necessary to access data from the storage media. The primary reason for the slow nature of, for example, an optical storage disk drive, is the time required to mechanically position the optics which are used to direct the beam of light to and from the appropriate positions on the surface of the optical storage media. An additional factor increasing the access times of optical storage disk drives is the rotational latency of the disk as it turns to bring the desired portion of the disk proximate the reading optics. Most current systems use a carriage assembly which holds various mirrors and optics and which is mechanically positioned over a section of the optical storage disk, for example. Data accessing must then wait for the optical disk to mechanically rotate to the desired section. The positioning of these carriage assemblies accounts for the first order term of the delay in accessing the optical storage media. The rotational latency accounts for the second order delay term.
Accordingly, a need has arisen for an optical tracking system which eliminates the need for the mechanical positioning of a carriage assembly and/or eliminating rotational latency and therefore reduces the time required to access the data stored in an optical storage media.